During dusk, the atmosphere is enriched with the excitement and activities of crows. They fly agitatedly and caw loudly, circling the sky animatedly. This situation is not unique to Singapore. New York is currently facing the same problem.[4]
The crows even caused trouble during the night. https://www.asiaone.com/singapore/2-gangs-fighting-bishan-residents-complain-noise-over-200-crows
During the day, the crows gather in large numbers in this open area. Crows are intelligent and social birds which live in extended family groups. They gather to feed on insects, worms, small animals, carrions, seeds, fruits and human-linked foods. These non-native birds are highly adapted to urban Singapore.
Their droppings mess up the sidewalks below where they gather and roost in large numbers. They are constantly engaged in intra and interspecific conflicts. https://www.humanesociety.org/resources/what-do-about-crows
On 11 December 2024, approximately 70 crows were seen holding a conference (probably) to discuss the next course of action as two of their family members were inside this enclosure (See Image 2).
I estimated the enclosure to have the dimensions 3m x 2.5m x 1.8m (L x W x H).
These were the number and type of birds I noticed on these days:
Attacks by crows have been reported in Housing Board Estates around Singapore over the years. Read the following articles:
This type of bird-trap is also known as the ladder and nets model. Many specifications and dimensions are used around the world. The link https://mothership.sg/2022/06/crow-culling-singapore-ladder-trap/ shows a man (probably from a bird management company) using a variant of this model to capture crows. He caught 7 of them and took the birds away expertly.
In the article from NORTH-WESTERN JOURNAL OF ZOOLOGY 14 (1): 85-90 Article No.: e171602, ‘Corvid control in urban environments: a comparison of trap types‘, different types of bird traps: Bow trap, Larsen trap, Swedish trap and ladder entrance trap were evaluated and compared for effectiveness. https://real.mtak.hu/90403/1/KoverL_etalLengyelsSz_NWJZ_OA.pdf
https://wildlife.onlinelibrary.wiley.com/doi/full/10.1002/wsb.1535 ‘Trapping efficacy of invasive crows is affected by environmental factors and deployment history‘ discussed the trapping effectiveness of the ladder and nets cage.
Both articles above discussed the difficulties of trapping corvids in an urban environment, chief of which is disturbance or harassment by humans. The traps are more effective in a high-density corvid area and the intelligent birds learn to avoid the traps after a while. Juveniles and adults are caught.
NParks follows international guidelines on humane pest bird and animal management. In earlier years, shooters were engaged to cull the birds. The corvids learnt to fly away at sounds and sights of the guns. The birds also became agitated when they spotted people carrying long umbrellas. This method is now considered hazardous to innocent people in a high rise urban environment. Read https://www.todayonline.com/singapore/ex-auxiliary-police-officer-jailed-culling-crows-shotgun-without-safety-officer-present
References:
1. https://extension.psu.edu/managing-urban-crow-roosts-in-pennsylvania-and-the-northeast
2. https://real.mtak.hu/90403/1/KoverL_etalLengyelsSz_NWJZ_OA.pdf NORTH-WESTERN JOURNAL OF ZOOLOGY 14 (1): 85-90 Article No.: e171602 ‘Corvid control in urban environments: a comparison of trap types’ by László KÖVÉR1,*, Norbert TÓTH1, Szabolcs LENGYEL2 and Lajos JUHÁSZ1
3. https://wildlife.onlinelibrary.wiley.com/doi/full/10.1002/wsb.1535 ‘Trapping efficacy of invasive crows is affected by environmental factors and deployment history’ by Cheryl K.L. Yong, Malcolm C.K. Soh, Astri Noorbaini Samsuri, Kai Ning Lim and Kenneth B.H. Er
4. https://www.vice.com/en/article/new-york-is-fighting-its-annual-christmas-battle-against-20000-crows/ by Luis Prada
Dave
17 December 2024
Bishan, Singapore
Update on 22 December 2024
The trap was removed on 20/12/2024. On the days that I walked past the structure I observed between 2-4 crows and 3-5 mynahs. On one occasion, I noted a dead mynah inside which was removed the following day. As I did not observe the birds being removed, I am unable to conclude how many birds have been trapped.
Simultaneous to setting up the trap, the leafy trees where the crows nest in large numbers had their crowns trimmed and the nests removed.
I will observe the crows over the next few days to see if they will disperse from this area.
